The present invention relates to apparatus and methods for inserting an intraocular lens through a small incision into an eye. More particularly, the invention relates to such apparatus and methods wherein the desired rotational orientation of the lens as it is inserted in the eye is easily, controllably and effectively achieved.
An intraocular lens (IOL) is implanted in the eye, for example, as a replacement for the natural crystalline lens after cataract surgery or to alter the optical properties of (provide vision correction to) an eye in which the natural lens remains. IOLs often include an optic, and preferably at least one flexible fixation member or haptic, which extends from the optic and becomes affixed in the eye to secure the lens in position. The optic normally includes an optically clear lens. Implantation of such IOLs into the eye involves making an incision in the eye. Making the incision as small as possible reduces trauma and speeds healing.
IOLs are known which are foldable (deformable) so that the IOL can be inserted into the eye through an incision smaller than the diameter of the lens and subsequently permitted to unfold after it has passed through the incision. A substantial number of instruments have been devised to aid in inserting such a foldable lens into the eye. The advantages of the foldable lens in cataract removal and lens replacement are so significant that many of the lens replacement procedures are performed with folded lenses inserted into the eye, and released therein to assume their initial unfolded state.
The success of foldable IOLs is enhanced by the surgeon's ability to control the orientation of the IOL during lens insertion. An IOL which is not correctly oriented as it is released from the inserter apparatus into the eye may require relatively difficult reorientation and/or can damage one or more parts of the eye. The risk of eye damage is particularly apparent in situations where the leading or superior fixation member or haptic, for example, comprising an elongated filament, is not properly oriented as it exits the insertion apparatus.
Some of the most generally accepted insertion apparatus employ a hollow insertion tube having a diameter which permits the folded IOL to pass freely through the tube without permanent deformation, and without causing the surgeon to apply excessive force to overcome friction between the walls of the insertion tube and the IOL. Excessive force can result in the premature ejection of the IOL before the surgeon is ready to position it within the patient's eye.
Unfortunately, the folded IOL tends to rotate axially within the insertion tube in an unpredictable manner as the IOL is moved distally through the tube prior to ejection. This means that the surgeon does not know what the orientation of the IOL will be upon its release from the insertion tube. As explained above, it is advisable for the surgeon to have control of the orientation of the IOL as it exits the insertion tube. Despite the many modifications of IOL injection devices, more precise control of the rotation of the IOL within the insertion tube and of the orientation of the IOL as it is ejected from the insertion tube remains a continuing goal.
It would be advantageous to provide IOL insertion apparatus and methods which facilitate the passage of a folded IOL through the apparatus in a controlled manner to achieve the desired orientation as the IOL is released into the eye.
It would be further advantageous to provide IOL insertion apparatus and methods which control the extent of rotation of the folded IOL during the insertion so that the surgeon knows or can predict the positioning of the IOL within the eye and/or reduce the risk of damaging the eye as the IOL is released into the eye.